Consider the molecule 4-amino- N -(2-aminoethyl)benzamide, which contains three distinct nitrogen atoms labelled as follows: (a) The nitrogen of the terminal aliphatic primary amine group (b) The nitrogen of the amide group (c) The nitrogen of the aromatic primary amine group What is the correct decreasing order of basic strength of these labelled nitrogen atoms?

Step-by-step solution

The basicity of a nitrogen atom depends on the availability of its lone pair for protonation. Nitrogen (a) belongs to an aliphatic primary amine. Its lone pair is localized and its electron density is increased by the +I effect of the alkyl chain, making it the most basic site. Nitrogen (c) belongs to an aromatic primary amine (aniline derivative). Its lone pair is delocalized into the benzene ring via resonance, making it less basic than the aliphatic amine. Nitrogen (b) belongs to an amide group. Its lone pair is